, didn't know that about DukeN3d (pretty cool), but the Unreal 1 I mean was like a real Portal portal/teleport. It could be my nostaligia blinding me a bit, but iirc you could really look through it (like a real view /not like flat tv) and also fire projectiles etc. through it. I remember seeing it in only 1 map, which looks similar to UT 1's Codex. My brother also remembers how well it looked so I know atleast it was not a dream. He even remembered reading something like that they changed the portals/teleports for UT 1 cause the Unreal 1 were to heavy on the computer. (dont quote me on that though)

Edit: found it I think http://s37.photobucket.com/user/BrainStorm_wow/media/UT3/tele.jpg.html

Also perhaps read this (although it seems to be more about using the ut3 editor) -> https://forums.epicgames.com/threads/717287-How-do-you-make-Classic-Unreal-Tournament-teleporters